KR101349827B1 - A method for transmitting beam forming information and a method for tracking position of a mobile station in multiple input multiple output system using codebook based beam forming scheme - Google Patents

Abstract

This document discloses a method for transmitting feedback information in a codebook-based multiple input / output system. For example, in a multiple input / output system to which a codebook based beamforming technique is applied, a method of transmitting beamforming information includes receiving a signal, estimating a reception channel, and transferring a phase shift matrix having a phase value as a variable. And transmitting the selected beamforming information through the estimated channel information in a codebook updated using the beamforming information.

MIMO, beam forming, feedback, code book, location tracking

Description

A method for transmitting beamforming information and a method for tracking the position of a mobile terminal in a multiple input / output system applying a codebook-based beamforming technique multiple input multiple output system using codebook based beam forming scheme}

This document relates to a multiple input / output system applying a codebook based beamforming technique. More specifically, in a multiple input / output system applying a codebook based beamforming technique, a method of transmitting beamforming information and tracking the location of a mobile terminal It's about how to do it.

Recently, demands for wireless communication services are rapidly increasing due to the generalization of information communication services, the emergence of various multimedia services, and the emergence of high quality services. To cope with this actively, the capacity of the communication system must be increased.In order to increase the communication capacity in the wireless communication environment, a method of finding new available frequency bands and increasing the efficiency of limited resources can be considered. have. In order to increase the efficiency of the limited resources among them, the transceiver is equipped with a plurality of antennas to obtain additional spatial area for resource utilization to obtain diversity gain or transmit data in parallel through each antenna. The so-called multi-antenna transmission and reception technology for increasing the capacity has been actively developed recently with great attention.

In a multi-antenna OFDM system, various techniques are required to increase data transmission reliability. Among them, a space-time code (STC) scheme and a cyclic delay diversity scheme are used to increase the spatial diversity gain. Diversity; CDD). In addition, techniques for increasing signal to noise ratio (SNR) include beam forming (BF), precoding, and the like. Here, beamforming and precoding are used to maximize the signal-to-noise ratio through the corresponding feedback information in a closed-loop system that can use the feedback information at the transmitting end.

The MIMO precoding scheme is one of multiple input / output system schemes for improving communication performance by feeding back channel information partially or entirely to a base station or a terminal in a closed-loop manner. This is particularly advantageous in a slow fading environment of 30 Km or less.

Examples of precoding techniques in closed-loop systems include a method of quantizing and feeding back channel information and a codebook based precoding method used when the feedback information is finite. . The codebook-based precoding is a method of obtaining a signal-to-noise ratio (SNR) gain by feeding back an index of a precoding matrix known to the transmitter / receiver to the transmitter.

Examples of the beam forming scheme may include a general beamforming scheme, a codebook based beamforming scheme, and a scheme using a combination of beamforming and MIMO techniques.

FIG. 1 is a view for explaining an example of a beamforming technique, and shows a beam pattern shape formed through each antenna when using the beamforming technique.

First, (a) of FIG. 1 shows a beam shape formed through each antenna when using a general beamforming technique. General beamforming is an adaptive beamforming scheme in which a weight vector for beamforming of a transmission antenna is updated according to a direction of arrival (DoA). For example, the optimal antenna weight may be obtained using the Wiener solution obtained through the Wiener equation, and the received SNR performance may be improved by removing signals from unnecessary directions.

1 (b) shows a beam shape formed through each antenna when using a codebook based beamforming technique. Codebook based beamforming is simple in configuration as shown in (b) of FIG. 1 and may correspond to fixed beamforming. This technique improves performance by allowing many users to select the optimal beam at the same time. An example of the codebook may be a codebook based on a Discrete Fourier Transform (DFT) matrix.

In addition, (c) of FIG. 1 shows a beam shape formed through each antenna when using a combination of beamforming and MIMO techniques. In particular, in this case, as shown in (c) of FIG. 1, an X-pol antenna having an X shape may be used to simultaneously support the existing MIMO scheme and beamforming.

Frequency division multiplexing (FDD duplex mode), which uses separate frequency bands for uplink / downlink channel transmission, has a difference in uplink / downlink channel characteristics for antenna weight calculation. Therefore, when the beamforming method is applied, gain loss may occur because antenna weight generation for beamforming based on the accurate channel estimation result is not performed. In addition, among the beamforming schemes described above, in particular, in the case of using a combination of a codebook-based beamforming technique and a beamforming and MIMO technique, as shown in (b) and (c) of FIG. As a result, a blind spot may be generated away from the beam and disappearing from the signal.

In addition, when the antenna feedbacks the antenna weight from the terminal to the base station in a closed loop scheme, excessive overhead may occur. Although the feedback overhead may be reduced to some extent based on the codebook, errors due to quantization errors and feedback delays that may occur in quantizing channel information may not be ignored. In order to alleviate the limitation of codebook use, recent researches have been conducted to reduce the error caused by quantization error or feedback delay and feedback overhead by flexibly changing the components of the codebook according to the channel variation of the time or frequency axis. .

In the prior art as described above, an object of the present invention is to provide a codebook updating method for updating and using a codebook in a codebook-based multiple input / output system.

Another object of the present invention is to provide a method for transmitting beamforming information in a multiple input / output system to which a codebook based beamforming technique is applied.

Another object of the present invention is to provide a method for tracking the location of a mobile terminal in a multiple input / output system to which a codebook based beamforming technique is applied.

In an embodiment of the present invention for achieving the above object, in a multiple input / output system to which a codebook-based beamforming technique is applied, a method for transmitting beamforming information includes: receiving a signal and estimating a reception channel And transmitting the selected beamforming information through the estimated channel information in a codebook updated using a phase shift matrix having a phase value as a variable and previous beamforming information.

The beamforming information may be codeword index information included in the codebook. The codebook determines a plurality of phase shift matrices by determining a plurality of phase values, multiplies each of the determined phase shift matrices by a vector component according to channel information to determine a codebook codeword, and determines the determined codebook codewords. It may be configured to include.

Here, each of the phase values may be determined by adding or subtracting an integer multiple of the phase interval based on at least one of a straight line connecting the transmitter and the receiver and the channel information. In addition, the phase interval may be generated by equally dividing a predetermined phase range by a number corresponding to the number of feedback bits.

인 선형 (Linear) 안테나일 수 있다.In addition, the beamforming information transmission method may be repeated a predetermined number of times. Each of the phase values may be reset to 0 ° with a preset repetition period. In addition, the plurality of antennas provided in the transmitting end for the multiple input and output, the interval between each antenna is

It may be a linear antenna.

When the codebook is updated by reflecting the channel state through the operation in the codebook update mode disclosed in this document, and a specific codeword having good reception performance is selected and fed back from the updated codebook, the channel is constantly changed without increasing the feedback overhead. Reflecting feedback information can be transmitted to improve communication performance.

In addition, by using a codeword value previously fed back when a codebook is updated and determining a new codeword value based on the codeword, a location tracking function of a mobile terminal in a multiple input / output system applying a codebook based beamforming technique is also used. You can expect a useful effect.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description set forth below in conjunction with the appended drawings is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details for a better understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. For example, in the following description, certain terms are mainly described, but they need not be limited to these terms, and they may have the same meaning when they are referred to as arbitrary terms.

In some instances, well-known structures and / or devices may be omitted to avoid obscuring the concepts of the present invention, and may be represented in block diagrams and / or flowchart diagrams centered on the core functions of each structure and / or device have. In the following description, the same components are denoted by the same reference numerals throughout the specification.

The following embodiments are a combination of the components and features of the present invention in a predetermined form. Each component or feature shall be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to construct embodiments of the present invention by combining some of the elements and / or features. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

In this document, embodiments of the present invention have been described based on data transmission / reception relations between a base station and a terminal. Here, the BS has a meaning as a terminal node of a network that directly communicates with the MS. The particular operation described herein as performed by the base station may be performed by an upper node of the base station, as the case may be. That is, it is apparent that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station can be performed by a network node other than the base station or the base station. A 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. The term 'terminal' may be replaced with terms such as User Equipment (UE), Mobile Station (MS), and Mobile Subscriber Station (MSS).

The present invention provides a codebook update method that can reflect channel variation in a multiple input / output system for transmitting feedback information using a codebook. In a system using a codebook based precoding scheme, the codebook update method may be applied to tracking of precoding that may reflect a channel state. In addition, in a system applying a codebook-based beamforming technique, it can also be used for location tracking of a terminal that can reflect the movement of the terminal. In the following, each vector component constituting the codebook is called a codeword.

In this embodiment, the current channel state can be reflected by using an extension matrix including a plurality of vector components in the codebook update. In this case, the codebook used for the previous transmission or the codeword of the codebook is used so that the codebook update can be made based on the previous transmission. The channel variation may be reflected by selecting and transmitting a codeword in consideration of the channel characteristics of the signal received in the updated codebook.

Hereinafter, as an example of the present invention, a codebook updating method using a phase shift matrix including a phase value as a variable as an extension matrix and a DFT unitary matrix forming a beam pattern orthogonal to each other as a base matrix will be described.

Equation 1 below shows an example of a phase shift matrix including a phase value as a variable.

는 위상값을 나타낸다. 위상값

은 소정의 규칙에 따라 결정된다. Equation 1 specifically represents a phase shift matrix that can be used when the number of rows of the base matrix is N. In Equation (1)

Represents a phase value. Phase value

Is determined according to a predetermined rule.

를 결정하는 일 방법을 설명한다. 예를 들어, 위상값을 결정하기 위한 소정의 위상범위를 결정한다 그리고, 위상범위를 K 개만큼 균등 분할함 으로써 일 위상간격을 결정할 수 있다. 이로써 각 위상값은

는 결정된 위상범위 및 위상간격을 이용하여 결정할 수 있다. 이하 수학식 2는 이러한 위상값 결정 방법의 일례를 수학식으로 나타낸 것이다. 수학식 2는 각 위상값을 위상범위를 균등분할 하는 값으로 정의된 위상간격의 정수 배로 결정하는 예를 나타낸 것이다.Phase value

Describes one way to determine. For example, a predetermined phase range for determining the phase value is determined, and one phase interval can be determined by equally dividing the phase range by K pieces. This ensures that each phase value

May be determined using the determined phase range and phase interval. Equation 2 below shows an example of the method of determining the phase value by the equation. Equation 2 shows an example of determining each phase value as an integer multiple of the phase interval defined as a value that equally divides the phase range.

과 같이 결정하고 결정된 위상범위를 K로 균등하게 분할하여 일 위상간격을 정의하여 이용하는 예를 나타낸다. 여기서, N과 K는 임의의 실수 값이다. 예를 들어, 위상범위는 송수신 안테나 소자의 수 또는 간격 빔패턴의 수 등에 따라 결정될 수 있다. Equation 2 is a phase range

As shown in the following, an example is used to define one phase interval by dividing the determined phase range equally by K. FIG. Where N and K are arbitrary real values. For example, the phase range may be determined according to the number of transmission / reception antenna elements or the number of interval beam patterns.

를 결정하는 다른 방법을 설명한다. 결정되는 위상값의 수는 코드북에 포함될 수 있는 코드워드 수가 될 수 있다. 예를 들어, 피드백 비트 수가 M인 경우 M 비트로 나타낼 수 있는 채널 상태의 수 즉, 코드북에 포함될 수 있는 코드워드 수는

이 될 것이다. 따라서, 이때 위상값의 수는 L 개가 될 것이다

.Phase value

Explain other ways to determine. The number of phase values determined may be the number of codewords that may be included in the codebook. For example, when the number of feedback bits is M, the number of channel states that can be represented by M bits, that is, the number of codewords that can be included in the codebook

. Therefore, the number of phase values will be L at this time.

.

This may be expressed as Equation 3 below.

The phase value determined at 0 ° or the previous transmission may be set as an initial value, and each phase value may be determined by adding or subtracting an integer multiple of the phase interval determined based on the initial value. This can be expressed as Equation 4 below.

은 0°또는 이전 전송 때 결정되었던 위상값을 중심으로 좌, 우로 고르게 분포할 수 있을 것이다. In Equation 4, t represents an index associated with the number of codebook updates and may be an integer value of 1 or more. When the value of t is 1, that is, the first codebook update, the value may be 0 °. As can be seen from Equation 4, the phase value is determined using this method.

0 may be evenly distributed left and right around the phase value determined at 0 ° or previous transmission.

In addition, in Equation 4, the f (i) value may be used by arbitrarily selecting L pieces of integer values from -L / 2 to L / 2. For example, the i value may be an integer value from-(L / 2-1) to L / 2 or -L / 2 to L / 2-1. In this case, there will be an advantage that the same phase value as the previous phase value can be selected in the codebook update mode. And for another example, the i value can be an integer value from-(L / 2-1) to -1 and from 1 to L / 2. In this case, it is not possible to select the same phase value as the previous phase value in the codebook update mode, but there may be an advantage that a more extended phase value can be selected.

Through the above-described method, a plurality of phase values may be determined to generate a phase shift matrix corresponding to each phase value, and the codebook may be updated by updating the codebook.

Equation 5 below represents a DFT unitary matrix forming beam patterns that are orthogonal to each other.

로 구성되는

는 수학식 5와 같이 나타낼 수 있다.Here, N is an integer value that determines the number of rows. For example, N may be determined according to the number of transmitting antenna elements in the case of precoding. In the case of beamforming, the beamforming may be determined according to the number of beam patterns. N columns vector

Consisting of

May be expressed as in Equation 5.

Hereinafter, the codebook update method according to the present invention will be described using the above-described phase shift matrix and DFT matrix.

의 코드워드 즉, 열 벡터 중 수신된 신호를 기초로 수신성능이 가장 좋은 코드워드

를 선택한다. 여기서 k는 코드북 내 코드워드 인덱스 값으로

의 값을 가질 수 있다. First, even if you do not perform a codebook update, or if you decide to perform a codebook update, the first codebook is the default codebook.

Codeword of which the best performance is received based on the received signal among the column vectors

. Where k is the codeword index value in the codebook

It can have a value of.

의 위상값

를 중심으로 소정의 위상범위

내에서 코드북 크기 N에 해당되는 만큼의 일정한 좌우 대칭의 위상 간격을 가지는 다수의 위상값에 따라 다수의 위상천이 행렬을 생성한다. 생성된 각 위상천이 행렬은 수학식 6과 같이 나타낼 수 있다.When operating in the codebook update mode, a plurality of phase shift matrices may be generated to update the existing codebook to reflect the channel state of the currently received signal or the movement of the terminal. At this time, as described above, the codeword used in the previous transmission

Phase value of

Predetermined phase range around

A plurality of phase shift matrices are generated according to a plurality of phase values having a constant left-right symmetrical phase interval corresponding to the codebook size N within the apparatus. Each generated phase shift matrix may be represented by Equation 6.

를 선택한다. The updated codebook may be generated by applying a plurality of phase shift matrices generated to the codewords used in the previous transmission. The codeword is selected by selecting the codeword having the best reception performance based on the received signal using the updated codebook.

.

The codebook update operation may be repeatedly performed several times. Hereinafter, the codebook update method described above will be generalized to describe an example of the codebook update operation from t times to t + 1 times through an equation.

Equation 7 below shows an example of a codebook update method that may be generated in a t-time codebook update operation.

에서 t는 코드북 갱신 횟수를 나타내는 값으로 첫 번째 코드북 갱신 동작에서의 t 값을 1로 시작하여 1씩 증가하는 정수 값이 된다. 그리고

는 이전의 즉, t-1회 코드북 갱신 동작에서 갱신된 코드북에서 선택되었던 코드워드를 나타내며 여기서, k는 코드북 내 코드워드 인덱스 값으로

의 값을 가질 수 있다. Equation (7)

T is a value indicating the number of codebook updates, and is a integer value starting at 1 and incrementing by 1 in the first codebook update operation. And

Denotes the codeword that was selected from the codebook updated in the previous, i.e., t-1 codebook update operation, where k is the codeword index value in the codebook.

It can have a value of.

In this case, in the case of using Equation 3 and Equation 4 as the method for determining the phase value, the updated codebook of Equation 7 may be represented as Equation 8a or Equation 8b.

Equation 8a indicates an updated codebook including the case where the phase value is 0 ° and Equation 8b indicates the updated codebook except when the phase value is 0 °. The advantages for each case are as described in equation (4). In Equation 8a, one maximum phase value having a negative value is excluded. Alternatively, one maximum phase value having a positive value may be excluded.

을 이용하여 수신된 신호를 기초로 수신성능이 가장 좋은 코드워드 예를 들어

를 선택한다.Updated codebook generated as in Equation 8a or 8b

For example, a codeword having the best reception performance based on a signal received using

.

Equation 9 below shows an example of a codebook update method that may be generated in a t + 1 codebook update operation.

에서 t는 코드북 갱신 횟수를 나타 내는 값으로 첫 번째 코드북 갱신 동작에서의 t 값을 1로 시작하여 1씩 증가하는 정수 값이 된다. 그리고

는 이전의 즉, t회 코드북 갱신 동작에서 갱신된 코드북에서 선택되었던 코드워드를 나타내며 여기서, k는 코드북 내 코드워드 인덱스 값으로

의 값을 가질 수 있다. Here too, the equation (7)

T is a value indicating the number of codebook updates, and is an integer value starting at 1 and incrementing by 1 from the first codebook update operation. And

Denotes a codeword that has been selected from a codebook updated earlier, i.e., in t codebook update operations, where k is the codeword index value in the codebook.

It can have a value of.

In this case, in the case of using Equation 3 and Equation 4 as the method for determining the phase value, the updated codebook of Equation 9 may be represented as Equation 10a and Equation 10b.

Equation 10a indicates an updated codebook including the case where the phase value is 0 ° and Equation 10b indicates the updated codebook except when the phase value is 0 °. The advantages for each case are as described in equation (4). In Equation 10a, one maximum phase value having a negative value is excluded, but one maximum phase value having a positive value may be excluded in another manner.

을 이용하여 수신된 신호를 기초로 수신성능이 가장 좋은 코드워드 예를 들어,

를 선택한다.Updated codebook generated as in Equation 10a or Equation 10b

For example, the codeword having the best reception performance based on the received signal.

.

Perform the codebook update operation several times by operating in the codebook update mode described above. To prevent an error that may occur, after performing a preset number of codebook update operations, a default DFT codebook matrix is used or a phase value is changed. You can reset it to 0 ° and start a new codebook update at the origin again. Alternatively, the predetermined threshold may be preset, and when the reception performance of the UE becomes worse than the preset threshold, the default DFT codebook matrix may be used to start the codebook update again at the origin.

Due to the movement of the terminal or the change of the communication environment, the value of the codebook codeword suitable for the current channel state also changes. In particular, in the case of beamforming, the direction of a desired beam is changed by the movement of the terminal. Therefore, when the codebook is updated to reflect the channel state through the operation in the codebook update mode according to the present embodiment, and a specific codeword having good reception performance is selected and fed back from the updated codebook, the codebook is changed every time without increasing the feedback overhead. Feedback information reflecting the channel may be transmitted, thereby improving communication performance.

In addition, by using a codeword value previously fed back when a codebook is updated and determining a new codeword value based on the codeword, a location tracking function of a mobile terminal in a multiple input / output system applying a codebook based beamforming technique is also used. You can expect a useful effect.

In addition, in the case of applying the codebook-based MIMO precoding or diversity scheme or the case of applying the codebook-based beamforming technique, the basic technical characteristics of the method of updating the codebook to perform feedback will be shared. If it is difficult to take the antenna configuration in common due to the different from each other will be able to configure and use each separately. In addition, the parameter values such as the phase range, the phase interval, the maximum value of the codebook update number, and the like will be applied to the optimized values according to the system and the communication environment, rather than fixedly using any specified value.

인 선형 (Linear) 안테나를 사용할 수 있다.An example in which the above-described codebook update method is applied to a codebook based beamforming technique will be described. When the codebook update method is applied to the codebook-based beamforming technique, since the location of the terminal can be tracked in consideration of the mobility of the terminal, the location tracking method may be referred to as described above. At this time, the interval of each of the plurality of antennas provided in the transmitting end is

Linear antenna can be used.

The present embodiment relates to a case of applying a codebook based beamforming technique, and may perform beamforming and / or location tracking using a DFT matrix and a location tracking matrix according to the number of antennas. In addition, since a common reference signal (RS) is used for channel estimation, it is not necessary to transmit a separate dedicated RS or a dedicated pilot channel for beamforming. In addition, since the information about the channel is fed back into the index by configuring the codebook, the channel state information is estimated from the upstream channel as in the conventional beamforming scheme of the frequency division multiplexing method. I can solve it. In addition, since the direction of a desired beam is also changed due to the movement of the terminal, the beamforming codebook is updated by the above-described method, and the position tracking according to the movement of the terminal is performed by applying an antenna weight for beamforming using the updated codebook. You can do it.

은

(여기서

은 송신 안테나 및/또는 가상 빔포밍 패턴 수) 값 중에서 결정될 수 있을 것이다. 그리고, 위상값

을 결정함에 있어서, 상술한 바와 같이 일정 범위의 각도

에 대해 좌, 우로 코드북의 크기로 분할하여 위상간격

을 결정할 수 있다. 그리고 0°또는 이전 피드백 전송 때 결정되었던 위상값을 초기값으로 하고, 이 초기값을 중심으로 위상간격의 정수 배만큼을 가감하여 각 위상값을 결정할 수 있다. 특히 빔포밍의 경우 위치 추적을 하고자 하는 단말과 기지국을 일직선을 일정 범위의 각도

의 중심인 0°로 설정하고 위치 추적을 시작할 수 있다.In the case of applying the above-described codebook updating method to beamforming, a phase value

silver

(here

May be determined from a number of transmit antennas and / or virtual beamforming patterns). And phase value

In determining, as described above, a range of angles

Phase spacing by dividing the codebook into left and right sizes for

Can be determined. The phase value determined at the time of 0 ° or previous feedback transmission may be set as an initial value, and each phase value may be determined by adding or subtracting an integer multiple of the phase interval based on the initial value. Especially, in the case of beamforming, the angle between the terminal and the base station to be tracked in a straight line is in a certain range.

You can set the position to 0 °, the center of the, and start tracking the position.

를 선택하고, 다시

를 중심으로 좌, 우 대칭으로 다시 일정 탐색범위에 해당하는 위상각도,

내에서 코드북 크기에 해당되는 만큼의 일정한 좌우 대칭의 위상 간격

을 가지는 빔 패턴을 생성하는 코드 북으로 갱신할 수 있다. 그리고, 갱신된 코드북에서 선택된 코드워드에 해당하는 안테나 가중치를 적용하여 빔을 형성함으로써 이동 단말의 위치 추적을 구현할 수 있다.That is, when the above-described codebook updating method is applied to the location tracking of the mobile terminal, first, the reception performance of the codeword of the beamforming codebook is the best at the receiving end.

Select it, and

Phase angle corresponding to a certain search range again in left and right symmetry with respect to

Constant symmetrical phase spacing within the codebook size within

It can be updated with a codebook for generating a beam pattern with. In addition, location tracking of the mobile terminal may be implemented by forming a beam by applying an antenna weight corresponding to a codeword selected from the updated codebook.

In this way, the process of updating the codebook may be repeated several times. Perform several positioning operations by using the above-described positioning method, but in order to prevent an error which may occur, after performing a predetermined number of positioning operations, use a basic DFT codebook matrix or set the phase value to 0 °. You can reset it to start the location tracking again from the origin. Alternatively, a predetermined threshold may be set in advance, and when the reception performance of the UE becomes worse than the preset threshold, the basic DFT codebook matrix may be used to start location tracking again at the origin.

2 is a flowchart illustrating a method of performing location tracking of a mobile terminal in a transmitting terminal according to an embodiment of the present invention.

The transmitting end first receives feedback information from the receiving end, for example, the corresponding terminal, in step S100. The feedback information may be codeword index information of a codebook. As shown in step S120, the codeword is selected from the basic codebook based on the feedback information, the antenna weight for the codeword selected in S121 is multiplied by the transmission signal, and the remaining processing is performed to transmit the signal. Here, the basic codebook may use a DFT matrix.

The codebook is updated in step S130. For example, the codebook is updated using a plurality of phase shift matrices having the codeword and the phase value selected in step S120 as variables. In this case, the method of updating the codebook may use a method of determining a plurality of phase values, generating a phase shift matrix for each of the determined phase values, and multiplying the generated phase shift matrix by the codeword selected in step S120. Such a codebook update method may be shared with the receiving end so that the codebook update method can be updated with the same rule.

이 될 것이므로 8개의 위상값을 결정하여 8개의 위상천이 행렬을 생성할 수 있다.The number of phase values may be determined as a number corresponding to the number of feedback bits. For example, if the number of feedback bits is 3 bits, the channel state that can be transmitted in 3 bits is

Since eight phase values are determined, eight phase shift matrices can be generated.

The receiving end will feed back the selected codeword from the updated codebook. Then, the transmitting end receives the feedback signal in step S140 and selects the codeword from the updated codebook for location tracking of the mobile terminal. The signal is transmitted by multiplying the antenna weights for the codeword selected in step S151.

Using the updated codebook, beamforming may be performed by multiplying an antenna weight to which location tracking of a mobile terminal is applied. In the case where the codebook update is continuously performed, the codebook update may be continuously performed based on the previous transmission until a predetermined number of times. FIG. 2 shows a case in which the codebook update count is set to P times and the codebook is continuously updated based on the codeword selected immediately before the Pbookcode update count is reached.

That is, for example, the codebook is updated again in step S130 to perform the codebook update again. The method of updating the codebook is similar to the case of step S130 described above. However, in this case, unlike the case of step S130 described above, it will be updated using the codeword selected in step S150. Through the codebook update operation, the codebook update considering the movement of the terminal is performed without additional feedback overhead.

When the number of codebook updates is a preset number of times, for example, P times in step S160, the codebook is selected again based on the basic codebook in step S120 and codebook updating is performed again. This is to have the opportunity of error correction due to the cumulative codebook update as described above. This initialization process may be described as resetting the phase of the phase shift matrix to 0 ° at a constant repetition period P interval.

In addition, the codebook size L and the phase interval according to the number of feedback bits in the codebook update mode, the number of repetitions P for resetting the codebook phase value, and the codeword index transmission period to be fed back are codebook updated according to the channel condition and fed back. It is desirable to design optimally in consideration of various factors such as the overhead amount of the codeword index.

3 is a flowchart illustrating a method of performing location tracking of a mobile terminal at a receiving end according to an embodiment of the present invention.

The receiving end first receives a signal transmitted from the transmitting end in step S200 and estimates a channel based on the received signal. In this case, the signal used for channel estimation may be a common RS as described above.

The optimum codeword is selected from the basic codebook through the channel estimated in step S220, and the codeword information selected in step S221 is fed back to the transmitter.

The codebook is updated in the same manner as the codebook updating method described above at the transmitting end. That is, a codebook capable of forming a beam reflecting a plurality of phase values near the beam generated by the previous feedback may be generated using the phase shift matrix and the codeword selected in step S220.

In step S240, the signal is received again and channel estimation is performed based on the signal. The optimal codeword is selected from the codebook updated in step S230 based on the channel information estimated in step S250, and the codeword information selected in step S251 is fed back to the transmitter.

When the number of codebook updates is a preset number of times, for example, P times in step S260, the codebook is again selected based on the basic codebook in step S220 and codebook updating is performed again. This is to have the opportunity of error correction due to the cumulative codebook update as described above. This initialization process may be described as resetting the phase of the phase shift matrix to 0 ° at a constant repetition period P interval.

4 is a diagram for explaining an example of a structure of a transmitter according to an embodiment of the present invention.

The transmitter for applying the beamforming technique includes a plurality of antennas 40, a beamforming position tracking controller 41, a mapper 42, a beamforming generator 43, and a modem 44 for performing multiple input / output. It is made, including.

Signals or feedback information from the receiving end may be transmitted through the plurality of antennas 40. In addition, the position tracking for the mobile terminal may be performed based on the feedback information received through the beamforming position tracking control unit 41. That is, the codebook update may be performed by the beamforming position tracking controller 41. In addition, the mapper 42 may reconstruct an array of signals in accordance with the IFFT conversion to convert the transmission data into OFDM signals and signals for multiple antennas. In addition, the beamforming generator 43 may multiply the antenna weight generated by the beamforming position tracking controller 41 by the transmission data for each antenna output from the mapper. Then, the transmission data multiplied by the antenna weight is then performed by the modem unit 44 to perform IFFT to convert the frequency axis signal into a time axis signal to be transmitted to the plurality of antennas (40).

It is clear that the claims that are not expressly cited in the claims may be combined to form an embodiment or be included in a new claim by an amendment after the application.

Embodiments in accordance with the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In a hardware implementation, in a codebook-based multiple input / output system according to an embodiment of the present invention, a method for transmitting feedback information and a method for transmitting precoding information may include one or more application specific integrated circuits (ASICs). , Digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, in a codebook-based multiple input / output system according to an embodiment of the present invention, the method for transmitting feedback information and the method for transmitting precoding information perform the functions or operations described above. It can be implemented in the form of modules, procedures, functions, and the like. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

1 is a flow chart illustrating a method of performing a beamforming technique.

2 is a flowchart illustrating a method for performing location tracking of a mobile terminal in a transmitting end according to an embodiment of the present invention.

3 is a flowchart illustrating a method of performing location tracking of a mobile terminal at a receiving end according to an embodiment of the present invention.

4 is a view for explaining an example of the structure of the transmitting and receiving end that can be applied to an embodiment of the present invention.

Claims (9)

In a multiple input / output system to which a codebook based beamforming technique is applied, a method of transmitting beamforming information may include: Estimating a receiving channel by receiving a signal; And Transmitting selected beamforming information over the estimated receive channel in a codebook updated using a plurality of phase shift matrices and previous beamforming information, Each of the plurality of phase shift matrices has a phase value as a variable, Each of the plurality of phase shift matrices is determined by determining the phase value, The codebook codeword is determined by multiplying each of the determined phase shift matrices with a vector component according to the estimated reception channel, The codebook is configured to include the determined codebook codeword, beamforming information transmission method. The method of claim 1, wherein the beamforming information, And codeword index information included in the codebook. The method of claim 1, And the phase value is determined by adding or subtracting the estimated reception channel and a straight line connecting the transmitting side and the receiving side by an integer multiple of the phase interval. The method of claim 3, wherein And the phase interval is generated by equally dividing a predetermined phase range by a number corresponding to the number of feedback bits. The method of claim 1, And the phase value is reset to 0 ° with a predetermined repetition period. The method of claim 1, The beamforming information transmission method may be repeated a predetermined number of times. delete delete delete

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